First, I know that I should and must use btrfs on my cache pool.  However, I also used it on my array or host drives.  I should have done more homework on this.  I looked a bit at ZFS, but I do like GUI's and I hate Oracle with a passion so said, "Ok I'll go btrfs".  I should have looked a xfs more and found out why it was the default during setup, but I didn't.

 

Now a week later and I read an Ars Technica article about btrfs and how it does raid and it scared the crap out of me.  Not sure about linking on the forum so if you want to read the article you can look it up on their site.  In short, the article gives some very good examples of why btrfs is a pain at least, and catastrophic at worst when you have raid issues.

 

So, I decided I needed a better understanding of how Unraid NAS features work under the hood as I think Unraid isn't using btrfs raid for redundancy in the array.  If that's the case then btrfs should be fine to use "I think!".  However, the only thing I can find about Unraid under the hood it that "It's like a MAID (Massive Array of Individual Disks), but that's it. I can find anything else.

 

So, I'm writing this (sorry for the length) post, and I hope someone can give a brief explanation on how the NAS features of Unraid work.  Why btrfs is or isn't an issue?  Why is xfs recommended over btrfs assuming it still is?  Thanks.

BTRFS in the array are individual files systems, which even that article (that pulls no punches) says is fine.

From what little I could find I thought that was the case.  Thanks for the conformation.  I do think it's too bad the Unraid devs don't have a high level architectural document somewhere so that it wasn't such a black box. At least for people like me that worry about things like that.

Turns out I'm and idiot.  I finally found Spaceinvaders excellent video explaining how Unraid parity works. https://youtu.be/HybwCOVDg9k

 

From what I now know after doing my homework, in regards to my original question about using BTRFS on the array drives, I see no good reason to do it.  BTRFS will not hurt anything but XFS would be a simpler, faster, and better choice.  IMO BTRFS should only be used on the cache pool in Unraid. Hopefully this will help someone that had the same question about using BTRFS that I had.

 

On an unrelated note BTRFS is great for your Linux laptop or workstation which is why I thought of using it on Unraid.  So, use it there but not on Unraid array drives.

 

28 minutes ago, docfallingapart said:

using BTRFS on the array drives, I see no good reason to do it.  BTRFS will not hurt anything but XFS would be a simpler, faster, and better choice.

Any solid evidence ?

I don't think XFS will perform better in array so far, I use Btrfs at day one in array or UD ( single or RAID ) no problem in general.

 

Unraid slow performance issue is user space FUSE layer, not much relate which file system use.

Edited September 28, 20214 yr by Vr2Io

None what so ever.  As I said it's just my opinion. Also, I'm using BTRFS on my array.  It's not worth doing it over as like you said BTRFS is fine and will work. However, if I could go back in time three weeks, I would have gone with XFS as I don't see any plus of using BTRFS on Unraid.  Most of the cool features that make BTRFS great on a desktop, just don't apply on Unraid.  As least as far as I've figured out in the limited time I've been doing this.  I am an Unraid noob for sure so I"m hardly authoritative on the matter.  If you see some benefit to using BTRFS on Unraid, please share it with the group, for the next guy that is just getting started.

5 hours ago, docfallingapart said:

Most of the cool features that make BTRFS great on a desktop, just don't apply on Unraid.

Depends on what you use, I rely on btrfs for data corruption detection and use snapshots together with send/receive to backup all my servers, but I do agree that the typical Unraid user who probably doesn't care or is not going to use these feature should use xfs for the array.